Sahih Bukhari Volume 3, Book 29, Hadith Number 71.

Narated By Ibn ‘Abbas : The Prophet fixed Dhul-Hulaifa as the Miqat (the place for assuming Ihram) for the people of Medina, and Qaran-al-Manazil for the people of Najd, and Yalamlam for the people of Yemen. These Mawaqit are for those people and also for those who come through these Mawaqit (from places other than the above-mentioned) with the intention of (performing) Hajj and Umra. And those living inside these Mawaqit can assume Ihram from the place where they start; even the people of Mecca can assume Ihram from Mecca.